A report into an academic fraud scandal at the University of North Carolina released on Wednesday found that for 18 years two academic advisers ran a program of fake classes that helped many athletes at the school remain eligible to play sports.

The report does not incriminate any coaches or athletic administrators in the scheme, carried out by two people within the African and Afro-American Studies department.

The "irregular classes," at UNC-Chapel Hill from 1993 to 2011, had no class attendance or faculty involvement, according to the independent investigation conducted by former federal prosecutor Kenneth Wainstein.

Over the course of their nearly two-decade existence, the classes affected 3,100 out of 97,600 undergraduate students who were enrolled at the university. Student-athletes accounted for 47.6 percent of enrollments in the irregular classes, the report found.

Many of the student-athletes were directed to the classes by counselors in the Academic Support Program for Student-Athletes, the report said, adding that various personnel at the school were aware of red flags, yet did not ask questions.

"Mr. Wainstein has found that the wrongdoing at Carolina lasted much longer and affected more students than previously known," UNC-Chapel Hill Chancellor Carol Folt said in a statement.

"The bad actions of a few and the inaction of others failed the University's students, faculty and alumni, and undermined the institution as a whole.

"This conduct could and should have been stopped much earlier by individuals in positions of influence and oversight, and others could have sounded the alarm more forcefully."